It is known to bind the protruding ends of weft threads into an auxiliary selvage with the aid of auxiliary warp threads. The auxiliary selvage is separated from the fabric itself. The formation of the auxiliary selvage takes place simultaneously with the beat up of the weft threads. The weft threads inserted into the loom shed have such a length, that the leading end of the weft thread at the exit end of the weft thread insertion channel passes a weft thread monitor, which is an integral part of the beat up reed. The weft thread monitor generates a signal that informs the central loom control regarding the proper weft thread insertion into the loom shed. The continued weaving operation is controlled by these weft thread monitor signals. As long as these signals remain uninterrupted, a proper weaving operation is assured.
Due to technological requirements the weft thread ends protrude from the outer edge of the auxiliary selvage. These protruding ends of the weft threads are subject to pneumatic turbulences due to the pneumatic of the weft thread into the weft channel insertion in an air loom. These turbulences of the weft thread ends cause a problem in that the weft thread ends of weft threads that have already been beat up, can be bound into the fabric during the next beat-up or shed change. Such binding of protruding weft thread ends into the fabric is unintended and results in fabric faults, which in turn reduce the fabric quality, even if later on efforts are made to pull the bound-in weft thread ends out of the fabric.
It is also known to center the weft thread ends by exposing these ends to a suction flow generated by a suction nozzle directed into the area of the turbulence. The suction nozzle thus tries to suck off the air causing the turbulence. Such a suction operation has not yielded a satisfactory result, because, on the one hand, the suction nozzle cannot be brought close enough to the free weft thread ends due to the limited available space at the exit end of the weft thread insertion channel and because on the other hand a relatively large volume of air must be sucked in by the suction nozzle. Additionally, such a suction nozzle involves a substantial structural effort and expense. Thus, economic and technical reasons militate against controlling the turbulence problem at the exit of the weft thread insertion channel by means of suction nozzles.
Another problem caused by fluttering weft thread ends resides in the fact that these ends cause disturbances in the automatic sequence of the weaving operation. For example, such turbulent weft thread ends can lead to the interruption of the light barriers that form part of the above mentioned weft thread monitors, so that a signal will be generated indicating that a weft thread was not properly inserted, which leads to a substantial interruption, especially in looms comprising a device for an automatic weft thread break removal. It is possible, that an automatic weft thread removal due to a break in the weft thread may be interrupted by a fluttering weft thread end, which must be avoided.